Question

An electric iron of power 1.5$kW$ is used for30 minute, to press the clothes Calculate the electrical energy consumed in (a) kilowatt hour (b) joule

Answer 1

$P=\frac{w}{t}\therefore$ Electrical energy $W=P\times t$
$P=1.5kWt=30$ minute $=\frac{30}{60}=\frac{1}{2}hr$
$1.5\times \frac{1}{2}=0.75kwh$
(b) $1kWh=3.6\times {10}^{6}J$
$\therefore 75kWh=0.75\times 3.6\times {10}^6$
$=2.700\times {10}^6$
$=2.7\times {10}^{6}J$